Fabrication and characterization of poly(vinyl alcohol)/ montmorillonite/poly(styrene sulfonic acid) proton-conducting composite membranes for direct methanol fuel cells

摘要

A high performance poly(vinyl alcohol)/montmorillonite/poly(styrene sulfonic acid) (PVA/ MMT/PSSA) proton-conducting composite membrane was fabricated by a solution casting method. The characteristic properties of these blend composite membranes were investigated by using thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, methanol permeability measurement, and the AC impedance method. The ionic conductivities for the composite membranes are in the order of 10~(-3) S cm~(-1) at ambient temperature. There are two proton sources used on this novel composite membrane: the modified MMT fillers and PSSA polymer, both materials all contain the -SO_3 H group. Therefore, the ionic conductivity was greatly enhanced. The methanol permeabilities of PVA/MMT/PSSA composite membranes is of the order of 10~(-7) cm~2 s~(-1). It is due to the excellent methanol barrier properties of the PVA polymer. The peak power densities of the air-breathing direct methanol fuel cells (DMFCs) with 1M, 2M, 4M CH_3OH fuels were 14.22, 20.00, and 13.09 mW cm~(-2), respectively, at ambient conditions. The direct methanol fuel cell with this composite polymer membrane exhibited good electrochemical performance. The proposed PVA/MMT/PSSA composite membrane is therefore a potential candidate for future applications in DMFC.